Hi there, I am currently working on a hat I got the pattern from someone on ravelry this is where I am stuck. What does WS and RS stand for? And what does 10 (11,12) mean I don't understand the numbers. Thank you.

Those numbers represent the different sizes. It's giving you a choice of which size. If you are working on the smallest size, then you use the smallest number. If you are making the middle size, then you would use the number that's on the left inside the parentheses. Same for the largest size.

It all depends on what size you're making. I would recommend making a copy of the instructions and taking a pencil and circling the correct number every tiime you see that little "group" thing, all the way through the pattern, so you don't lose track.